Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$143.95	9.482%	$157.5993	$157.60	$157.60	$157.60
Purchase #2	$150.70	7.536%	$162.0568	$162.06	$162.05	$162.10
Purchase #3	$57.51	10.680%	$63.6521	$63.65	$63.65	$63.70
Purchase #4	$127.65	12.449%	$143.5411	$143.54	$143.55	$143.50
Purchase #5	$93.58	7.850%	$100.926	$100.93	$100.95	$100.90
Purchase #6	$191.25	7.382%	$205.3681	$205.37	$205.35	$205.40
Purchase #7	$35.81	6.388%	$38.0975	$38.10	$38.10	$38.10
7 purchase totals =	$800.45		$871.2409	$871.25	$871.25	$871.30